1. Field of the Invention
This invention relates to the formation of an external flare around the end of a metal tube. More particularly, the invention is concerned with flaring the end of a tube of substantially elliptical cross-section having helical corrugations along its length.
2. Description of Related Art
Elliptical tubes having helical corrugations are widely used as waveguides in the RF/microwave industry. When the elliptical tube is used as a waveguide, the end may be flared to, for example, squarely abut a waveguide connector or splice in order to establish electrical contact between the waveguide and the connector or splice. To enable good electrical contact between the waveguide and the connector or splice, it is desirable for the flare to be free of cracks and of substantially uniform thickness.
Prior screw press and or hammer type flare tools are typically intended for use with tubular tubing, for example electrical conduit, where they operate on a symmetrical end surface. When these flare tools are used with elliptical cross-section tubing having helical corrugations, the tubing end must be repeatedly worked and or hammered, making it difficult to prepare an acceptable flare without a considerable time investment by a skilled metalworker. The presence of helical corrugations on the tube further complicates formation of an acceptable flare.
Previously available flare tools designed specifically for forming flares in elliptical tubing have been relatively expensive and require separate time consuming operations with a plurality of tools to form an acceptable flare. U.S. Pat. No. 4,590,785, by John P. Morris, assigned to Andrew Corporation as is the present invention, describes a flare tool set for elliptical tubing comprising a pair of screw press type flaring tools; one dimensioned for the major axis, the longer dimension of the ellipse, and another dimensioned for the minor axis, the shorter dimension of the ellipse. Each of the tools must be attached and applied in turn to form a single flare.
Competition within the waveguide industry has focused attention on equipment and personnel costs, as well as time requirements for installation and maintenance of waveguide systems.
Therefore, it is an object of the invention to provide an apparatus that overcomes deficiencies in the prior art.